Multiple gain stages - how much where?

Well, there are 5 opamps each with a GBW of 1 GHz, or 1.8 if we use the THS parts. But end-to-end, I "only" have a gain of 1e5 and a bandwidth of 100 MHz or so. That sort of defines the oscillation hazard.

PSRR goes to hell at high frequencies (we use one opamp that has GAIN from one power rail to the output) so I guess I should filter some of the power supplies to some of the opamps.

John

Oh, okay.

The only argument I've heard that makes _any_ possible sense contrarywise, and I don't buy it yet, is the idea of quantum entanglement and the multiverse. So I take the point.

We throw words around about concepts we don't even understand, but think we do. What we need to do is look to see where nature shows us dividing lines... not where we decide to make them. As in why Pluto isn't a planet, now --

5 orders of magnitude of "nothing" along a useful scale that was uncovered separates the other planets in our solar system from Pluto, which is why. Look for what nature shows, not what we like to imagine.

There probably is a substantial base of noise underlying thought. So... well, that may modify a little of what you are writing there.

Ego. Weird thing is, religious folks I argue with often try and say how "humble" they are before God and try to play up all this 'insignificance' and 'humbleness' about themselves as though that makes what they say still stronger and anything an atheist says must be somehow egotistical. Just the opposite is true. They are lying to themselves and others and really think they are VERY IMPORTANT and the center of some supreme being's attentions. And there is nothing of humbleness in anything they say, despite the words they use. By comparison, atheists really do see themselves as tiny bits of meaningless matter in a vast universe of meaninglessness and just try to find meaning by helping others get by in the small life they have.

:)

I suppose it depends. Not every species on Earth is equally viscious. I can at least imagine the case where aliens have survived _because_ they worked out the important memes in their social system that allowed that survival and they might, if they aren't too human about it, apply such morality more broadly with us the unknowing beneficiaries.

Of course, I don't think it is likely. Just a thought.

Jon

n the

upling

--
> =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 =A0 =A018pf =A0 =A0 =A0| =A0/
> =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 =A0 =A0| -
> =A0 =A0 =A0 =A050nh =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0|/
> =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 =A0 =A0 |
> =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 =A0 =A0 |
> =A0 =A0 =A0 gnd =A0 =A0 =A0 =A0 =A0 =A0 gnd

Never saw that before thanks.  Aren't you throwing away 1/2 the
signal?

George H.

>
> The pd pulse is so fast we need to slow it down a little before it
> hits the first opamp. This does it, and also presents a wideband 50r
> load to the pd input, to prevent reflections.
>
> John- Hide quoted text -
>
> - Show quoted text -

in the

oupling

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-------

For a diplexer would you take the output across the resistor.... switch the resistor / cap positions?

George H.

t- Hide quoted text -

machine

'in control'

something

those existed.

Then stop acting like an ape.

then ours).

--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

vicious.

Not the first nor the last time I'm likely to make that mistake.

Jon

Or viscous ?:-) ...Jim Thompson

-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

| 1962 |

The Ground Zero Mosque IS Appropriate When Renamed... The Obama Monument to American Impotence

No, it's a lowpass filter (1 ns tau, 160 MHz cutoff) in the signal path, gain of 1. It looks like 50 ohms to the input.

I think some old Tek scopes did this.

John

One wayI look at "gain structure" is to think about adjusting the gain of each stage so that they ALL clip at the same point.

I belive this means that most of the gain should go at the very beginning, if it is a high overall gain circuit.

boB

.

I do think we have free will, but only in the sense of being able to make unpredictable decisions. From an evolutionary point of view, always choosing the "best" solution makes you dangerously predictable, so we - or rather some fairly remote ancestor - evolved a random number generator that injected enough arbitrariness into the process of making decisions where the optimum choice isn't all that much better than the alternatives for us to be safely unpredictable.

t a machine

Except that evolution has had to work out how to inject a certain amount of randomness into the process to make it difficult for predators to predict what we are actually going to do next.

are 'in control'

know,

something

in

Except that for clocks, being predictable is a virtue. For potential dinners, it's a weakness.

Humans have evolved the knack of cooperating closely in groups of about 150 - a bigger number than any predatoiry pack animal can manage. Herds get safety in numbers by a different mechanism, and the members of a herd don't have to keep track of the behaviour of various individuals within the herd.

Language is one of the mechanisms we've evolved to help us achieve this. Computers and communications have enormously increased the power of language to facilitate communication, and I'm sure that we are evolving furiously at the moment to take full advantage of this increased power. The increased reproductive success of film stars and rock stars probably isn't the mechanism that will selectively enhance our capacity to cooperate in bigger and more geographically extended groups - other people are also doing well out of the new situation, and may be expected to rear more healthy and successful kids in consequence.

if those existed.

Depends on the aliens, and how they perceive their interests.

Who aren't much different from us, and consequently don't have much to offer.

nced then ours).

The space-flight technology would have to be. Different points of view can be very useful in understanding the universe, and intelligent aliens might value us as precisely that kind of resource.

-- Bill Sloman, Nijmegen

the

pling

About 15 years ago I did up to 10^4 of variable gain at up to a few MHz - two Burr-Brown (now TI) VGA810'a in sequence for the forward path and a pair of much slower (and cheaper) Linear Technology parts for the backward path to keep the DC operating point right in the short term - on a single small board. The idea was to offer photomultiplier-like gain flexibility with an infra-red-sensitive photo-diode for setting up laser systems.

I sweated blood analysing the feedback paths through the power pins, but my first layout worked fine. I had to add a 3.3pF capacitor to the original circuit because TI had failed to specifiy the 15pF input capacitance of one of the subsidiary op amps I'd used, but none of the stuff I'd been worried about gave me any trouble.

The guys that I designed it for took it away and I never heard another word, so presumably it did what they wanted for the brief period that they wanted it.

-- Bill Sloman, Nijmegen

he

ing

You mean the Percival distributed amplifier. He was working at EMI Central Research when he invented the idea in 1936. He was still working there in 1976-79 when I was there and I got to meet him. I can remember that we had a useful conversation about something work related, but I can't remember what we were talking about.

-- Bill Sloman, Nijmegen

machine

'in control'

something

Evolution is surely changing. Survival rates in poor countries are way up, due to simple things like vaccines and vitamins and improved agriculture. That reduces selection pressure.

What big cities and universities and Facebook are doing is to let the extreme outliers find each other. A village of 150 people won't produce a mating pair of six-sigma geniuses, but New York City does it routinely. So we can expect the distribution to grow long extended tails, and we can expect more consequences like autism as geeks breed with geeks.

On average, we're not evolving much, because there's not a lot of selection going on.

John

"John Larkin" wrote in message news: snipped-for-privacy@4ax.com...

Hard? You put a pole on top of a zero. That's third year college if I'm not mistaken :)

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

When cascading distributed amplifiers, optimum use of tubes results in a stage gain of e.

Distribured amps fell out of fashion when transistors came along, but are back big-time in the form of monolithic distributed gaasfet amps, with bandwidths like 20 and 40 GHz. They are used to drive e-o modulators in fiberoptic telecom systems.

John

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eel in

Evolution is going to keep on doing what it always did. Selection is going to be concentrated on what affects the number of your off-spring (and near relatives) who survive to have children of their own.

ccines and vitamins and improved agriculture. That reduces selection press= ure.

Less selection for resistance to infetious disease, and for features that will make less likely that you will starve to death if there is a shortage of food while you are still growing rapidly.

More selection for features that will make you look like a feasible breeding partner to the opposite sex.

Intelligence does seem to depend on a lot of different genes - and there seem to be a number of different ways of being a genius. The six- sigma genius couples that I know of only have three-sigma bright kids. Lee Kuan Yew of Singapore had similar ideas about the advantages of female graduate marrying male graduate and having lots of kids, but we haven't seen any flood of Singaporean super-geniuses in recent years

Only if we don't know what we are talking about.

Really? I've got no kids, my younger brother has five, and my youngest brother has three. That's a substantial difference in reproductive success.

-- Bill Sloman, Nijmegen

On a sunny day (Mon, 20 Sep 2010 19:03:12 -0700 (PDT)) it happened Bill Sloman wrote in :

I think you are falling back into that self-overestimating error ;-)

man

While you can only see aliens as a potential threat. Did you vote for Geert Wilders?

-- Bill Sloman, Nijmegen

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Hi John, The cap looked like a short to ground at higher frequencies... But you are looking at a pulse and just want to strech it.

It's interesting I use the same circuit configuration (R + inductor in parallel with R + capacitor) to compensate coils. Where R is the coil resistance, L the inductance and C is choosen so that RC =3D L/R. It makes the coil look like a pure resistance to the amp that is driving it.

(If you've got the voltage head room adding more R to both sides can help.)

George H.